Weird result for modulus operation

[Ang Way Chuang]

Paolo Bonzini wrote:
>>>>>>>  Thanks for the speedy reply. But why this code:
>>>>>>>
>>>>>>>         int a = 17, b = 16;
>>>>>>>         a = a++ % 16;
>>
>> Huh? Now you got me confused. Since it is an undefined behaviour, gcc 
>> is free to whatever it likes.
> 
> Sure, but if you ask gcc to signal a warning, it is supposed to do so. 
> :-)  It is a bug that gcc with -Wsequence-point signals a warning for "a 
> = a++ % 16" but not when you use abc.a.
> 

Oic, thank you for the clarification. I didn't notice that the warning 
works for a = a++ % 16 because I only tried the -Wsequence-point flag on 
abc.a example.

>> Though the answer given by the first and second examples show 
>> inconsistency in gcc in handling the undefined behaviour.
> 
> That's not a problem.  GCC does not have to be consistent.  But both 
> should be warned about.
> 
>> I can't forward to gmane.comp.gcc.devel newsgroup with my account.
> 
> No problem, you can delete it.
> 
> Paolo
>